Manufacture of phenols or salts thereof



Patented 19, 1948 5.51.99 MANUFACTURE OI PIIINOLS B SALTS rmaor DanielTyrer, stockton-on-Tees, England No Drawing. Application August 1, 1541,Serial n 765.651. In Great mum August 1:. 1m

' 1 This invention relates to the manufacture of phenols or saltsthereof from salts of the corresponding sulphonic acids. Subject mattercommon to the present specification and to the provisiohal and completespecifications filed by me in Great Britain August 13, 1942, and May 25,1943. for British Patent No. 559,642, is described and claimed herein,and with respect thereto the said British specifications are relied uponfor priority purposes under the provisions of R. S. 4887 as extended byPublic Law 690, 79th Congress, 35 U. S. C., sec. 101. Other subjectmatter of my said British specifications is disclosed and claimed in myU. 8. Patent No. 2,407,045, issued September 3, 1946, on applicationSer. No. 493,924 filed July 8, 1943, under the provisions of R. S. 4887.

The customary fusion process .ior the manufacture of phenols fromthecorresponding sulphonic acids involves fusing the sulphonic acid saltwith caustic alkali, and the reaction in the case of sodium benzensulphonate, which may be taken as typical. is as follows:

CeHsSOaNa+NaOH- CsHsONa+NaaSOa-l-H2O caustic soda are required accordingto theory,

whereas in practice not less than 7, and usually about 14, molecularproportions are used,

If it is attempted to carry out the fusion process by adding the alkalisulphonat to the theoretical quantity of fused caustic alkali thereaction mixture assumes an undesirable thick semi-fused condition. If,again, the theoretical quantities of alkali s phonate. and causticalkali are mixed together beforehand and subsequently heated to frothand swell up on reaching the reaction temperature.

7 I have now found that it is possible to produce phenols or saltsthereof from the corresponding alkali metal sulphonates by reaction withsubstantially the theoretical quantity of caustic alkali without theabove-mentioned disadvantages, it an intimate solid mixture or thereactants is prepared containing an additional solid particulatesubstance consisting of finely powdered carbon in such proportion,comprising at least 2 per cent. to about 30 per cent. of the weight ofthe sulphonic acid salt, that during the subsequent 6 Claims. (Cl.260-628) heating operation the reaction mixture does not froth or swelland remains in a substantially solid condition, and if the said solidmixture is heated at a temperature ranging from 350-400 C. to cause thesulphonic acid and caustic alkali to undergo reaction.

The term "phenols is used herein in describing the invention to includenaphthalenes and other hydroxyl-substituted aromatic or heterocycliccompounds which themselves and in the form of their correspondingsulphonates used as starting materials do not readily decompose or leadto side reaction at the reaction temperature required for the presentprocess. Among the more especially suitable phenols there may bementioned the hydroxy-benzenes, cresols, hydroxy-naphthalenes andhydroxy-pyr dines.

The term "caustic alkali" as used herein and in the appended claimsdenotes only sodium hydroxide or potassium hydroxide.

I have also found that the reaction may be conducted with theintroduction of steam, and that then, in the case of a large number ofphenols, the phenol, instead of remaining in the reaction residue as aphenolate, is removed from the reaction mixture by the steam in the formor the free phenol, and can be recovered from the aqueous condensateproduced by condensing the issuing vapours. By using this method ofoperation, in the case of phenols capable of being removed from thereaction mixture by the steam. only hall the quantity of caustic alkaliis required for the reaction, that is to say only one molecularproportion oi. caustic alkali for each sulphonate radical in thesulphonic acid salt. In the case or sodium benzene sulphonate andcaustic soda the reactionmay then be represented as follows:

bring about the reaction, the mixture tends to powdered carbon isnecessary, tempted to conduct the-reaction ctmsom +ri orr ctnton+misosHowever also in this case, the addition of finely for if it is atwith'the theoretical proportion of caustic soda without that addition, themixture on reaching the reaction temperature suddenly swells up to forma frothy mass of great volume.

In the case of a phenol which cannot be removed by steam it remainsinthe reaction residue in the form of phenoiate, whether steam isintroduced or not. When th reaction is conducted without steam, in thecase of phenols capable of being removed by steam, the bulk of thephenol remains in the reaction residue. as phenolate but a small amountis expelled as the free phenol with 's the water vapour produced duringthe reaction. and-may be recovered by condensins the issuing Byconducting the reaction in a closed vessel so that the water vapourcannot escape the whole of the phenol can be retained as phenolate inthe reaction residue. when the reaction is conducted so as to produce aphenolate. the latter may serve as a starting material for making otherproducts so that it is not always necessary to convert it into the freephenol.

It will be understood that the reaction should be conducted in theabsence: of air in order to prevent oxidation of the reactants or of theproducts formed. The introduction of steam serves as a convenient meansof securing this end. Alternatively, the reaction may be conducted in anatmosphere of hydrogen or other inert gas.

When the process is applied with the introduction of steam to themanufacture of phenols, such as phenol itself, which are capable ofbeing removed from the reaction mixture by stem, the

removal of the product from the reaction vessel as it is formed with thesteam constitutes a further advantage. In the case of phenols, such asresorc'inol, which cannot be removed by steam,

the normal theoretical quantity of caustic" alkali, that is to say twomolecular proportions per sulphonate radical, is required whether steamis introduced or not. The introduction of steam then serves as aconvenient means for excluding air from the reaction vessel, and alsoserves to remove any impurities of other phenols capable of removal bysteam.

In the case of phenols, such as fl-hydroxypyridine, which can beremovedby steam, but with greater diillculty than. say. phenol itself, a higherrate of introduction of steam is required to remove them but even thenthe removal is slower than in the case of phenol itself. With suchphenols a better expedient is to remove a part of the product with steamand recover the remainder from the reaction mixture. For this purposethe proportion of caustic alkali is reduced below the theoretical twomolecular proportions per sulphonate radical to an extent llpropriate towhatever proportion of the product it is desired to remove by steam. Forexample, 1.5 mols of caustic alkali will enable to per cent of thep-hydroxypyridine produced to be removed by steam.

From the foregoing description it will be understood that the expression"theoretical quantity of caustic alka is used herein and in the appended claims to denote the quantity which is theoretically requiredunder the conditions used.

namely according to whether steam is introduced or not, and, in theformer case, according to the amount of the phenol removed by the steam.

is 8-4 times the weight of the sulphonate undergoing reaction, but inthe case of phenols which are not very readily removed, such asp-hydrmpyridine, a somewhat higher rate is of advantage.

Although the use of steam is not essential in the process of theinvention, its use offers the following advantages: In the ,case ofphenols capable of being removed by steam, the theoretical quantityofcaustic alkali becomes one half of that required in the absence ofsteam. The product is obtained in association with water only. Bidereactioni are reduced or avoided b the rapid removal of the phenol fromthe reaction mixture. A. part or the wholeof the heat required for thereaction may be supplied by preheating the steam. It is also found thatthe use of steam leads to a speedier reaction.

Operating without the introduction of steam enables the phenolates,instead of the free phenols, to be produced, and enables a somewhatlower reaction temperature, for example 350' C. insteadofstil'ctobeused.

Any desired form of finely powdered carbon may be used, but onlypowdered coke is very suitable owing to its low cost. In the case ofcoke the ash content should be low, since the constituents of the ash.such as silica, will react to some extent with the caustic alkali. Thefiner the particle size of the carbon the smaller will be the quantitythereof required in the reaction mixture, and in general it is desirableto use material which is not coarser than will pass through a so meshsieve.

The particular proportion of finely powdered carbon, within theaforesaid range of 2 to 80 per cent... which is required to secure theabove described anti-frothins action varies with the nature of thereactants and the conditions of the of finely powdered coke.

In general it is advisable, however. to use more than the minimumaddition, for, while the latter prevents frothing and substantialfusion, incipient fusion or sinterins may occur which would hinder heremoval of the phenol when steam is used, a larger addition improves theporosity of the reaction mixture. A larger addition also facilitates thedrying of the mass when the reaction mixture is worked up into the formof a granular mass as described below. Generally speaking about 20-30per cent. of finely powdered carbon is satisfactory,.whether or notsteam is used.

The reaction is considerably assisted by ensuring that the reactants arein a state of intimate contact during the reaction. This intimateconmixture, evaporating the water completely or sufficiently to producea solid granular mass which will not soften or cake on heating due tothe presence of residual water. The soluble ingredients may be dissolvedwholly or partially in the water before evaporating to dryness. Aconvenient method of mixing the ingredients in the presence of water isto mix all theingredients, ex-

cept the caustic alkali together in dry powdered form, and then mix themwith a strong aqueous solution of the caustic alkali, themixture thenbeing evaporated to form a solid granular mass as describedabove. Theevaporation of the water may, if desired, be carried out wholly or inits final stages in thereaction vessel before starting the reaction.Another method of brinsing about kali sulphonate by the it will liewithin the the desired intimate contact is to briquette a mixture oi theingredients while. in a moist condition. In each of the foregoingmethods of mixing it is important to prevent the mixture from absorbingan appreciable amount of carbon dioxide from the atmosphere.

The alkali metal salt of the sulphonic acid may be the sodium orpotassium salt, and a mixture of both salts may be used. Either sodiumhydroxide or potassium hydroxide may be used as the caustic alkali. Thespeed oi the reaction is especially high in the case 01' potassiumsulphonates, and can beincreased in the case 01' any aladdition of apotassium salt, more especially potassium chloride. There may also bementioned potassium sulphite or potassium sulphate, each of which alsoacts as an anti-frothing agent. The use of a potassium salt as reactionaccelerator is especially advantageous with sodium sulphonates as theydo not react so rapidly as the potassium sulphonates. A very rapidreaction is obtained by reacting a potassium sulphonate with potassiumhydroxide. Accordingly, an acceleration of the reaction can be securedby ensuring that the reaction mixture has a content of alkali metalradical consisting at least in part of potassium.

With regard to the reaction temperature, it has been found that when amixture of 1 mol of sodium benzene sulphonate, 1 mol of caustic soda and25 per cent (calculated on the weight of the sulphonate) of finelypowdered coke of low ash content, is heated in a current of steam phenolbegins to form slowly at about 350 C. The reaction becomes rapid atabout 380 C. If 0.75 mol of potassium chloride is added to the abovemixture the speed of the reaction at 350 C. is about 15 times fasterthan it is without the potassium chloride. In general a temperature ofabout 380 C. gives a suitably rapid reaction. Although the most suitablereaction temperature depends to some extent on the particular sulphonateused, range of 350-400 C. It is of advantage to introduce the steam inpreheated condition. By preheating the steam to a temperature above thereaction temperature the whole or a part of the heat required may besupplied.

Owing to the diminution in the rate at which the phenol is produced asthe reactants are consumed, it is generally not of advantage to continuethe reaction after about 9095 per cent. oi. the sulphonate has beenconverted. The unchanged sulphonate can be used in a fresh treatment. Ifthe reaction is conducted as a continuous process by charging freshreactants into the reaction vessel to replace the materials consumed,the initial high rate of phenol production can then be substantiallymaintained throughout the process. When the process is conducted as abatch treatment with steam it is advisable to reduce the rate ofintroduction of the steam to correspond with the diminution in the rateof phenol production. I

The invention also includes the treatment of the reaction residuetoconvert alkali sulphite formed during the reaction into alkalisulphonate or caustic alkali or both for a fresh reaction, and torecover unchanged sulphonate and any added substances. 7

' In order to convert alkali sulphite into alkali sulphonate a solutionof the former may be treated with the tree sulphonic acid andthe'sulphur dioxide formed expelled by boiling. If the sulphonic acidcontains sulphuric acid the sulphateformed therefrom may be removed at alater Other methods of conversion T stage. Preferably, however,thesulphuric acid is removed by adding calcium hydroxide or recoveredcalcium sulphite. removing the precipitated calcium sulphate byfiltration, and adding alkali sulphite or alkali carbonate to thefiltrate to precipitate the residual calcium sulphate as calciumsulphite or calcium carbonate. Instead of the free sulphonic acid itscalcium or barium salt may be used, and the precipitated calcium orbarium sulphite is then removed from the alkali sulphonate solution.

In order to convert alkali sulphite into caustic alkali a solution orthe former may be boiled with calcium hydroxide or barium hydroxide.With a calcium hydroxide the conversion is only partial, but it isadvantageous owing to its low cost. As is well known the degree ofcausticisation depends on the concentration of the alkali sulphite, sothat by suitably adjusting the concentration the desired degree oiconversion can be obtained. The unchanged alkali sulphite can be readilydeposited by concentrating the solution and then removed. The unchangedsulphite so recovered maybe similarly treated to convert it into causticalkali. The partial causticisation produced by calcium hydroxide may besupplemented as desired by using barium hydroxide in addition.

example, sodium sulphite may be converted into caustic soda byelectrolysis in how manner.

When the reaction is conducted in steam with complete removal of thephenol formed, the reaction residue contains as soluble constituents,alkali sulphite, small quantities of caustic alkali and unchanged alkalisulphonate together with any potassium salt which may have been added toaccelerate the reaction. and as an insoluble constituent powered carbon.The reaction residue is taken up in water, and the carbon may be removedby filtration. tin order to prepare a fresh batch of reaction mixturethe resulting solution may be concentrated to cause the deposi tion of aquantity of the alkali sulphite such that sufllcient alkali sulphite andcaustic alkali remains in solution to produce the desired quantity ofsulphonate by reaction with sulphonic acid or alkaline earth sulphonateas described above. To the solution obtained after removing thedeposited alkali sulphite and regenerating the desired quantity ofsulphonate, there is added the necessary quantity oi caustic alkali andfinely powdered carbon. The latter may be the carbon which has beenremoved as described above, and subsequently dried. The caustic alkaliso added may, ii desired, be made by causticlsing as described above thealkali sulphite removed.

An alternative procedure is to add the required caustic alkali to thesolution of the reaction residue, and then deposit by concentration andremove a quantity of alkali sulphite equal to that which has been formedduring the reaction. A part of the latter is used to make the requiredsulphonate, and, if desired, the remainder may be used to make causticalkali.

Another alternative is to treat the reaction residue, after removing thecarbon. with sufllcient sulphonic acid to produce the alkali sulphonaterequired, and then to concentrate the solution in order to depositthealkali sulphite. The concentrating operation may be performed beforeor after adding the necessary quantity of caustic alkali, but it it isperformed after such addition the deposition of the alkali sulphite isfacilitated since the latter is less soluble in caustic alkali may beused, for

solution. The alkali sulphite so removed may be used for making thecaustic alkali.

A still further alternative is to divide the reaction residue into twoportions, one portion for making the alkali sulphonate and the otherbeing either treated for the preparation of caustic alkali or discardedand replaced by fresh caustic alkali.

A further and preferred method. however, is

to mix the reaction residue with water, and, with or without preliminaryfiltration. to boil the aqueous liquor at such a concentration and withsuch an addition of calcium hydroxide as are necessary to cause theformation of at least the greater part of the caustic alkali required.After filtering the liquor. the excess alkali sulphite is deposited byconcentrating the filtrate andis removed. The alkali sulphite so removedis used for preparing the necessary alkali sulphonate, and, if desired.for providing any additional requirement for caustic alkali. The alkalisulphonate solution so obtained is then mixed with the alkaline motherliquor. After suitably concentrating the mixed solutions, and adding thenecessary quantity of finely powdered carbon, the whole is evaporated toproduce a fresh reaction mixture of the original composition.

In the above methods any loss of alkali may be made good by the additionof fresh caustic alkali or alkali sulphite at a suitable stage in therocedure. I

The degree of ca'usticisation can be increased by adding additionalalkali sulphite to the aqueous extract of the reaction residue or somesurplus -alkali sulphite may be left in the reaction mixture as afloating stock. I

The aforesaid preferred method, in which the reaction residue iscausticised to produce the whole of the required caustic alkali. may beillustrated as applied to a reaction residue consisting, for example, ofi8 parts of unchanged sodium benzene sulphonate. 113 parts of sodiumsulphite. 4 quarts of unused caustic alkali and 45 parts of finelypowdered carbon (the parts being by weight). The residue is dissolved inwater. the carbon is removed by filtration. and the solution is adjustedto a concentration of 110-120 grams of sulphite per litre. The solutionis boiled with about 35 parts of calcium hydroxide. 50 per cent. ofv thesulphite is causticised giving a solution containing 40 parts of causticsoda and 58.5 parts of sodium sulphite. After filtration, the solutionis concentrated until substantially the whole of the latter sodiumsulphite has been deposited, which quantity is sumcient to prepare 162parts of sodiumbenzene sulphonatep- The latter are added to theconcentrate so as to produce a solution containing 180 parts of thesulphonate and 40 parts of caustic soda, which are the proportions ofthe constituents present in the original reaction mixture. It will beseen that only one half of the sodium sulphite has to be causticised toproduce the whole of the caustic soda required.

The sulphur dioxide which is liberated when aim: sulphite is treatedwith the free sulphonic acid to produce alkali sulphonate as describedabove may be used for making sulphuric acid for the production ofsulphonic acid. When the reaction has been conducted with theintroduction of steam, the quantityof sulphur dioxide so liberated istheoretically sufficient to furnish 50'per cent. of the sulphuric acidrequired. However, when the reactionis conducted without steam, thesulphur dioxide so liberated is preferably used for converting phenolateinto free phenolas 8 described below, and could only be used for makingsulphuric acid if some other acid, for example carbonic acid, were usedfor the latter conversion.

when the process is conducted without introducing steam, or when thephenol formed is not removed by the steam introduced, the phenol remainsin the reaction residue in the form of the phenolate. Before working upthe residue by one of the methods above described, it is desirable torecover the phenol therefrom. Forthis purpose the residue may be takenup with water. filtered to remove carbon, and the filtrate treated withan acid to decompose the phenolate. The liberated phenol may be removedin any suitable manner, for example, by simple physical separation, bydistillation or by extraction with a suitable solvent. In the case ofresorcinol it is advantageou'sly extracted with ether, the ether removedfrom the extract solution by distillation, and the crude productpurified by vacuum distillation.

Any suitable acid may be used for decomposing the phenolate. but it ispreferable to use the sulphite, as advantage can then be taken of itslow solubility in the alkaline solution.

- E'or working up the residue after the removal of the phenol the abovedescribed methods are applicable, but there are now an additional oneequivalent of alkali salt to be dealt with and an additional oneequivalent of caustic alkali to be restored,

The preferred method is to liberate the phenol by means of sulphurdioxide, and, after removing the phenol, to causticise sufilcient of thealkali suiphite with calcium hydroxide to yield the greater part or thewhole of the caustic soda After filtration, the solution is concentrateduntil sufilcient alkali s'ulphite is deposited for preparing therequired amount of sulphonate. When the free sulphonic acid is used forpreparing the sulphonate the sulphur dioxide 1iber-- ated is used fordecomposing the phenolate. if necessary, together with additionalsulphur dioxide. The sulphonate solution and the causticised solutionare combined and worked up into a fresh reaction mixture with theaddition of finely p wdered carbon.

"When the phenol produced is removed with steam. the mixture of thephenol and steam issuingfrom the reaction vessel is condensed and thecondensate may be worked up by known methods for recovering andpurifying the phenol. When the phenol is insoluble or only slightlysoiuble in water simple physical separation may.

sufilce. When it is appreciably soluble the portion in solution may berecovered by extraction with a solvent. In the case of phenol itself andmany other phenols extraction with benzene ora similar solvent issatisfactory, since the phenol is substantially wholly extracted therebyin a relatively dry state, and simple distillation sufiices to separateand recover the solvent.

The residual liquor remaining after the extraction, which may containsmall quantities of the -9 phenol. may be used for the generation ofsteam required for the process. The residual phenol and any of thesolvent which may be present may either be returned to the reactionvessel with the steam or concentrated as a residue in the still. In thelatter case caustic alkali may be added to ensure the retention of thephenol in the still liquor. The concentrated liquor from the still maythen be worked up by known methods for recovering the dissolved phenol.

Another method of dealing with the residual liquor remaining afterextraction is to use it for dissolving the reaction residue when thelatter is being worked up. Any residual phenol will then be returned tothe process with the reconstituted reaction mixture. During the reactionin the presence of steam the phenolate is decomposed into the freephenol and caustic alkali.

In some cases, for example, when p-hydroxypyridine is being made. thewhole oi the condensate containing the phenol may be transferred to thestill for generating steam and at the same time obtaining a phenolicconcentrate. Alternatively the condensate may be separately concentrated.by distilling the water.

As stated above, it is desirablethat the rate at which the steam ispassed through the reaction vessel should be kept low so as to obtain acondensate as rich as possible in the phenol. In the case of somephenols a further enrichment can be obtained by only partiallycondensing the vapours from the reaction vessel so as to produce acondensate having a higher concentration of the phenol. The uncondensedsteam may be returned to the reaction vessel for re-use.

The crude phenol obtained by the foregoing methods of recovery may bepurified in any suitable manner, for example, by distillation or bycrystallisation from a suitable solvent.

Owing to the repeated working up of the reaction residue to form freshreaction mixture the latter will become progressively contaminated withimpurities present in the materials or formed in the process. Forexample, the oxidation of sulphite to sulphate will tend to causeExample 1 100 parts of sodium benzene suphonate, 30 parts of potassiumchloride and 22.2 parts of caustic soda are mixed in aqueous solutionwith 25 parts of finely powdered coke. The mixture is evaporated whilestirring to produce a granular solid mass which does not soften onheating. The granular mass is heated in a reaction vessel at 380 C. in aslow current of preheated steam. The issuing vapours are condensed to amixture of phenol and water. After about one hour the production ofphenol is very slow andabout 90 per cent. of the sulphonate hasundergone reaction.

The aqueous condensate is extracted with benzene, the benzene is removedfrom the extract solution by distillation, and the phenol is rectifiedby distillation. Approximately 45 parts of phenol are obtained, whichrepresents a yield of 98 per cent. calculated on the sulphonate whichreacts. By recovering the small quantity of phenol which remains in theaqueous liquor after the extraction the yield is brought up to 97 percent.

The residue remaining in the reaction vessel is extracted with a minimumquantity of hot water. the solution is filtered to remove the coke, andthe filtrate is cooled, if required after concentration, to crystalliseout a portion of the sodium sulphite present. A sufllcient quantity ofbenzene sulphonic acid is added to the mother liquor to provide 100parts of the sodium sulphonate including the 10 parts of unchangedsulphonate already present. After boiling the solution to expel thesulphur dioxide the necessary quantitiesof caustic soda and finelypowdered coke for a further reaction are added, and the solution isevaporated as described above to provide a fresh batch of granularreaction mixture.

Alternatively, the reaction residue may be worked up as follows: Theresidue is mixed with a quantity of water sufllcient to form a solutioncontaining about 110 grams of sodium sulphite per litre. and 20 parts ofcalcium hydroxide are added. The mixture is boiled to .bring about thecausticisation of about half the sulphite by means of the calciumhydroxide. The calcium sulphite is removed by filtration, and thealkaline filtrate is concentrated until the bulk of the remaining sodiumsuphite is deposited. The latter is removed and boiled in solution with.79 parts of benzene sulphonic acid, whereby a solution containing partsof sodium benzene sulphonate is obtained. Should there be a deficiencyof sodium sulphite for this conversion, the deficiency is made up by theaddition oi fresh sodium sulphite or sodium carbonate. The resultingsulphonate solution, after suitable concentration, is mixed with thealkaline solution remaining after the removal of the sodium sulphite. 25parts of finely powdered coke are added to the mixture, which, aftermaking good any deficiency of caustic soda, is used for making a freshbatch oi reaction mixture.

Example 2 An aqueous solution containing 100 parts of potassium benzenesulphonate and 28.6 parts'of caustic potash is suitably concentrated andthen mixed with 20 parts of finely powdered coke to form a slurry. Theslurry is heated while stirring to produce a nearly dry granular solid,care -being taken to avoid the absorption of carbon dioxide from theair. The solid mixture is then heated in a reaction vessel so that thetemperature rises from 350 to 380 C. while a slow current of steam ispassed through the mixture at a rate of about 300 parts of steam perhour. The vapours which issue from the reaction vessel are condensed andform a milky suspension of phenol in water. After about 1% hours theproduction of phenol is very slow, and about per cent. of the sulphonatehas been converted into phenol, so that the reaction is stopped. Thecondensate contains approximately 42.5445 parts of phenol, the yieldbeing about 98 per cent. calculated on the sulphonate which undergoesreaction.

The condensate is extracted with about 100 parts of benzene, the benzenesolution is separated and distilled to recover the benzene. The phenolwhich remains behind is fairly pure and may be further purified bydistillation. The

ii. greater part oi the phenol is recovered in this ,way, the remainderbeing present in the aqueous I .residue left after the extraction withbenzene. This residual phenol may be recovered byusing the aqueousresidue to generate steam ior the process or may be returned to theprocess by using the aqueous residue to dissolve the solid reactionresidue. 1 p a The solid reaction residue, which contains about 78.5parts or potassium sulphiie is treated with a quantityoi. watersufiicient to produce-a .potassium sulphite solution having aconcentration of about 125' grams per litre. The mixture is filtered toremove the finely powdered coke, and

the filtrate is boiled after the addition 0120 parts or calciumhydroxide which causticises so much or the potassium sulphite as toproduce the original 28.6 parts 01' caustic potash. The calcium sulphiteis removed by filtration, and the filtrate is concentrated to depositthe unchanged potasslum sulphite.

The potassium sulphite thus deposited is used to prepare 95 parts oi.potassium benzene sulinto calcium sulphate. The mixture is boiled toexpel the sulphur dioxide produced, and then filtered to remove thecalcium sulphate. A very small quantity oi potassium suiphite orpotassium carbonate is added to the filtrate to precipitate the calciumsulphate remaining in solution. The solution is allowed to settle and isthen suitably concentrated. The concentrated solution is mixed with thecausticised solution. By adding parts or finely powdered coke to thecombined solutions the composition of the original reaction mixture isrestored.

, sample a 100 parts of sodium toluene sulphonate, eonsisting mainly ofthe ortho-compound; are mixed in aqueous solution with or potassiumchloride, 20.6 parts of caustic soda and parts of finely powdered coke.The mixture is evaporated to'dryness to produce a granular mass. Thelatter is heated in a slow current or steam at 380-390 C. Aiterabout 2%hours the production of cresols' becomes very slow and 90 per *cent oithe sulphonate has reacted. The product which is condensed together withthe steam is completely soluble in caustic soda solution.

The condensate is extracted with benzene. and the extract solution isdistilled. After-the distillation of thebenzene, 47.5 parts of cresolare obtained by distillation for the most part at the boiling point orortho-cresol. Only a trace of material boiling above the boiling point0! para- 'cresol is obtained. The yield of cresol exceeds 90 per cent ofthe converted sulphonate.

The sons reaction mixture is taken up in w s.

filtered to remove the finely powdered coke. and apart of the sodium.sulphite is removed from the filtrate by crystallisation. The motherliquor is then boiled with sumcient toluene sulphonic .acid to produce atotal of 100 parts oi the sodium salt, and the necessary quantity ofcaustic'soda ior a further reaction is added. The solution is then evaorated to provide a fresh batch of granular reaction mixture.

Alternatively, the reaction mixture may be worked up to regenerate thecaustic alkali in the manner described in the preceding examples.

- Sample 4 I 100 parts of potassium benzene-metadisulphonate containing8 per cent. of the monosulphonate are mixed in aqueous solution with'10, parts of caustic potash and evaporated with the addi- .tion of 30parts of finely powdered coke to produce a solid granular mass. Thelatter is heated at a temperature of 380 C. for 5-6 hours in a slowcurrent of steam. The condensate collected during this period containsabout 3.7 parts of phenol. The reaction residue is cooled out oi contactwith the air, taken up with hot water, and the aqueous mixture isfiltered to remove the coke. The filtrate is concentrated to a smallvolume to facilitate the subsequent extraction, and is then neutralizedby introducing sulphur dioxide gas. The mixture is filtered to remove alittle carbonaceous matter which separates, and the clear solution isexhaustively extracted with ether. After removing the ether and a littlewater by distilling the ethereal solution 28 parts of a crudeproduct areobtained which, on fractional distillation, yields approximately 23.5parts of substantially pure resorcinol leaving 4.5 parts of 'aby-product of high boiling point.

The aqueous mother liquor containing mail .ly potassium sulphite may beworked up as described in the preceding examples to prepare a ires batchof reaction mixture.

Example 5 100 parts or sodium naphthalene a-sulphonate are mixed inaqueous solution with 24 parts. of potassium chloride and 17.6 parts ofcaustic soda. 20 parts of finely powdered coke are added, and the wholeis evaporated to produce a solid granular mass, care being taken toavoid the absorption of carbon dioxide from the atmosphere. The granularmass is then heated at 370 C. in a slow current of superheated steam.and the issuing vapours are condensed to form a mixture of alpha-naphthol and water. After heating for about one hour the reactionpractically ceases and about per cent. or the sulphonate is converted.

The aqueous condensate is extracted with benzene, and the extractsolution is distilled to remove the benzene. The residue consists of 52parts of a-naphthol, which represents a yield of 92 per cent. on theconverted sulphonate. The

.product may be further purified by distillation under reduced pressure.

The reaction residue is extracted with water, filtered to remove thecoke and the filtrate is concentrated suiilciently to remove bycrystallisation a part of the sodium sulphite present. A solution ofcalcium naphthalene a-sulphonate is addodto the mother liquor in aquantity sumcient to produce a total of parts of the sodium sulphonate.The precipitated calcium sulphite is removed by filtration, thenecessary quantities oi caustic soda and finely powdered coke for afurther reaction are. added to the filtrate, and the latter is worked upinto a granular mass as described above to provide a fresh batch orreaction mixture.

Example 0 s naphthol is prepared from sodium naphthalene fi-sulphonateby the procedure described in Example 4. The. only difierences are thatthe temperature is 380-390- 0., and the reaction is stopped when 85 percent. of the p-sulphonate has reacted. since it is difilcult to carrythe reaction to the 0 per cent. stage. The above mentioned 13 85 percent. stage is reached after heating for 2-3 hours. The quantity ofcrude B-naphthol obtained after extracting with benzene amounts toapproximately 50 parts, representing a yield of 94 per cent. on theconverted sulphonate.

I claim:

1. A process for the manufacture of phenols or salts thereof whichcomprises, preparing an intimate solid mixture of an alkali metal saltof the sulphonic acid corresponding to the phenol desired, a causticalkali in substantially the theoretical quantity and an additionalparticulate solid substance consisting of finely powdered carbon in suchproportion, comprising at least 2 per cent. to about 30 per cent. of theweight of the sulphonic acid salt, that during the subsequent heatingoperation the reaction mixture does not froth or swell and remains in asubstantially solid condition, and then heating the said solid mixtureat a temperature ranging from 350 to 400 C.- to cause the sulphonic acidsalt and caustic alkali to undergo reaction.

2. A process for the manufacture of phenols or salts thereof whichcomprises, preparing an intimate solid mixture of an alkali metal saltof the sulphonic acid corresponding to the phenol desired, a causticalkali in substantially the theoretical quantity and an additionalparticulate solid substance consisting of finely powdered carbon in suchproportion, comprising at least 2 per cent. to about 30 per cent. of theweight of the sulphonic acid salt, that during the subsequent heatingoperation the reaction mixture does not froth or swell and remains in asubstantially solid condition, and then heating the said solid mixturein a current of steam at a temperature ranging from 350 to 400 C. tocause the sulphonic acid salt and caustic alkali to undergo reaction.

3. A process for the manufacture of phenols or salts thereof whichcomprises, mixing together in the presence of water an alkali metal saltof the sulphonic acid corresponding to the phenol desired, a causticalkali in substantially the theoretical quantity and an additionalparticulate solid substance consisting of finely divided carbon in suchproportion, comprising at least 2 per cent. to about 30 per cent. of theweight of the sulphonic acid salt, that during the subsequent heatingoperation the reaction mixture does not froth or swell and remains in asubstantially solid condition, stirring the mixture and simultaneouslyevaporating sufllcient water therefrom to produce a solid granular masswhich is incapable both of softening and caking on heating due to thepresence of water, and then heating the said granular mass in a currentof steam at a temperature ranging from 350 to 400 C. to cause thesulphonic acid salt and caustic alkali to undergo reaction.

4. A process for the manufacture of phenols or salts thereof whichcomprises, preparing a moist mixture of an alkali metal salt of the.sulphonic acid corresponding to the phenol desired, a caustic alkali insubstantially the theoretical quanw 2 per cent. to about 30 tity and anadditional particulate solid substance consisting of finely dividedcarbon in such proportion, comprising at least 2 per cent. to about 30per cent. of the weight of the sulphonic acid salt, that during thesubsequent heating operation the reaction mixture does not froth orswell and remains in a substantially solid condition, forming the moistmixture into briquettes, and then heating the said briquettes in acurrent of steam at a temperature ranging from 350 to 400 0-. to causethe sulphonic acid salt and caustic alkali to undergo reaction.

5. A process for the manufacture of phenols or salts thereof whichcomprises, preparing an intimate solid mixture of an alkali metal saltof the sulphonic acid corresponding to the phenol desired, a .causticalkali in substantially the theoretical quantity and an additionalparticulate solid substance consisting of finely powdered carbon in suchproportion, 2 per cent. to about 30 per cent. of the weight of. thesulphon'ic acid salt, that during the subsequent heating operationthereaction mixture does not froth or swell and remains in a substantially solid condition, preparing the said solid mixture so that itincludes a content of alkali metal radical consisting at least in partof potas-. sium, and then heating the at a temperature ranging from 350to 400 C. to cause the sulphonic acid salt and caustic alkali to undergoreaction.

6. A process for the manufacture of phenols or salts thereof whichcomprises, preparing an intimate solid mixture of the sulphonic acidcorresponding to the phenol desired, a. caustic alkali in substantiallythe theoretical quantity and an additional particulate solid substanceconsisting of finely. powdered carbon in such proportion, comprising atleast per cent. of the weight of the sulphonic acid salt. that duringthe subsequent heating operation the reaction mixture does not froth orswell and remains in a substantially solid condition, preparing the samesolid mixture so that it includes acontent of alkali metal radicalconsisting at least in part of potassium, and then heating the saidsolid mixture in a current of steam at a temperature ranging from 350 to400 C. to cause the sulphonic acid salt and caustic alkali to undergoreaction.

DANIEL TYRER,

REFERENCES one!) The following references are of record in the 559,642Great Britain Feb. 28, 1944 comprising at least' said solid mixture ofan alkali metal salt

